USB outlet and heater on starter batteries. Please help!

Flynt · 03-16-2023, 12:10 PM

I am currently trying to wire my diesel heater into my starter batteries so I can draw power from those while the bus is running. In the future it will also be attached to my solar setup so I can switch between the two. The problem I'm running into is getting the heater started. It requires 12v and 15amps to start up then 3amps continuously after its been started. I've tried wiring it to the main fuse box on my electrical panel (outlined in white on the attached image). It seems to work will the unit is in idle mode but as soon as I try to start it the power gets cut off. It has something to do with the unit underlined in red from my picture. There's a clicking noise inside it that seems to cut off power to everything. Could anyone explain to me what this part is for? Is there anyway to work around it? I've tried a few different fuse locations and they all seem to do the same thing. This also seems to be the same issue causing my usb charger to not draw enough power to charge my phone. I'm assuming its some sort of amperage limiter but I'm not sure how to work around it. I could wire things straight to the batteries but that doesn't seem very smart. Thanks in advance for any advice you can give me!

Dbacks2k4 · 03-16-2023, 02:43 PM

It's a solenoid. Gets turned on when key is on and off when key is off. That clicking noise you hear is the solenoid engaging and disengaging. A lot of buses have a second solenoid that are controlled by a switch in the drivers area called noise kill - basically they wire anything noisy like fans and radios to that one so the driver can turn them off quickly at railroad crossings to listen for trains.

Your fuses are usually tied in columns to always hot (not going through solenoid), on primary solenoid, and on noise kill solenoid.

It's common for them to be wired in a way that when the engine starter is cranking the solenoid is disconnected momentarily.

If you're saying the solenoid is cutting out when the diesel heater starter is engaging you could be overloading the solenoid, but I wouldn't think 15 amps should overload it. They do go bad frequently, you can buy replacement solenoids online for relatively cheap. I'd try swapping it out first.

If you don't want the diesel heater tied to the bus ignition at all go into a different fuse column that's not behind a solenoid.

Rwnielsen · 03-16-2023, 04:53 PM

Probably the easiest way is to tie into the load side of that solenoid and use the in-line fuse supplied with the heater. I think your problem is that you're hitching into the downstream side of a circuit breaker that can't carry the additional load. If you do go straight to the switched side of the solenoid, make sure to have the correctly sized fuse close to the connection. A starter battery can light up a section of #14 wire in seconds.

Flynt · 03-16-2023, 05:03 PM

I have tried attaching it to the load side of the solenoid but it still seems to trip it. Luckily the heater came with an in-line fuse so I can mess around with it that way. I guess its just a bad solenoid?

Flynt · 03-16-2023, 05:08 PM

Okay so I'm assuming the noise-kill is wired to my ignition when I turn it. I never had a noise kill switch anywhere else. I always wondered what that meant so thank you for that info.

Currently my coolant heater is tied into the noise-kill column and that's working fine but its just some low power fans. I was trying to wire the diesel heater into the 'always hot' column but that still trips the solenoid. So I guess I should just try a new solenoid? Is there any in particular or just one that looks the same? I found a 24v 50amp one that looks similar.

Rwnielsen · 03-16-2023, 05:25 PM

I'm not really understanding this...solenoids don't trip, they're simply a switch. The wiring controlling them is entirely independent. Is there a circuit breaker upstream of your solenoid that's tripping?

Flynt · 03-16-2023, 05:35 PM

Well whatever its doing is switching off power from wherever I try pulling it from. There is an additional smaller solenoid just below it that says 12v 5amps but it has wires going somewhere in the dash so I'm assuming its an independent system.

Rwnielsen · 03-16-2023, 07:04 PM

Quote:

Originally Posted by Flynt

Well whatever its doing is switching off power from wherever I try pulling it from. There is an additional smaller solenoid just below it that says 12v 5amps but it has wires going somewhere in the dash so I'm assuming its an independent system.

I understand this is a little frustrating but I'm just trying to get you hooked up and running with the key on. Another alternative would be hooking up to one of those larger wires at the top. Although those heaters don't draw much when they're off you'd still want to pull the fuse after the heater shuts down.

Flynt · 03-16-2023, 07:44 PM

Quote:

Originally Posted by Rwnielsen

I understand this is a little frustrating but I'm just trying to get you hooked up and running with the key on. Another alternative would be hooking up to one of those larger wires at the top. Although those heaters don't draw much when they're off you'd still want to pull the fuse after the heater shuts down.

Yeah so I've tried hooking it up to that positive terminal at the top left of the panel to no avail. I've also tried with the key in the ignition and turned. I maybe have not tried while the bus is running but that shouldn't matter right? Could there be a piece missing that separates the solenoid from the rest of the electrical? Though in that case I'd assume other things would be acting up as well. I did remove a lot of wiring for things I didn't need in the beginning but made sure to test everything each time. I'm not trying to be rude so I apologize if it comes off that way. I really do appreciate your help.

Rwnielsen · 03-16-2023, 08:16 PM

Quote:

Originally Posted by Flynt

Yeah so I've tried hooking it up to that positive terminal at the top left of the panel to no avail. I've also tried with the key in the ignition and turned. I maybe have not tried while the bus is running but that shouldn't matter right? Could there be a piece missing that separates the solenoid from the rest of the electrical? Though in that case I'd assume other things would be acting up as well. I did remove a lot of wiring for things I didn't need in the beginning but made sure to test everything each time. I'm not trying to be rude so I apologize if it comes off that way. I really do appreciate your help.

I troubleshoot electrical gremlins for a living and sometimes you just have to stop, back up and come at it with a different approach.
I have a Blue Bird bus. It has two solenoids, one comes on in acc. and they're both on in the ign position. I would be surprised if the one in your photo is rated at less than 100-150 amps. That being said...is it possible you have a loose connection on one of the larger wires? One that would read voltage and then go open under any significant load? The solenoids on my bus come directly from the batteries. The one in your picture shows two control points, one is a solid ground and the other is from your ignition switch. A test light would be really handy and the remote for your heater if you have one. Believe it or not, this is a simple problem.

Oh, and don't worry about sounding frustrated, Minnesota winters and all

Flynt · 03-16-2023, 08:39 PM

All the connections seem tight. I've been probing around with a multimeter and have the heater control right next to the panel so I can test it easily. I just don't really know what I'm looking for. Are the control points the two spots with all the wires attached at the top left of the panel? Or are you referring to the two bigger wires on the solenoid? I can see they both go to 2 out of the 3 bigger connections at the top of the fuse box but I don't understand how each of those points affects things.

Flynt · 03-16-2023, 08:42 PM

I see what you mean about it coming straight from the battery though. I can tell that there is a wire going from the main positive at the top left of the board to the middle (pwr 1) connection on the fuse box. Then that goes to the solenoid and out the other side to the left most connection on the fuse box. This is why I was so confused when it still cut out after trying to draw power from the main positive connection.

Rwnielsen · 03-16-2023, 10:01 PM

Quote:

Originally Posted by Flynt

I see what you mean about it coming straight from the battery though. I can tell that there is a wire going from the main positive at the top left of the board to the middle (pwr 1) connection on the fuse box. Then that goes to the solenoid and out the other side to the left most connection on the fuse box. This is why I was so confused when it still cut out after trying to draw power from the main positive connection.

That would indicate a bad connection. It will read full voltage and suddenly drop out when you apply a load. The only other thing I can think of at the moment is a bad connection in one of the Molex connectors in your heater wiring. There's a 3 pin going to the display, a 2 pin to the pump and the main junction is a 6 pin, at least on the three heaters I have. Maybe one of the pins has pulled out of the connector...

Flynt · 03-17-2023, 12:48 PM

I got it! Apparently the ground on the right side of the solenoid is what I needed to hook onto. It's not going anywhere else in the system... except for the fuse box which is also screwed into the main panel so it should or could all be on the same ground still??? I don't understand why the ground on the left side doesn't work... of course it does when I draw from that positive side of the solenoid but why would it cut out then? Would that mean it has a really low amperage limit?

Clouse House · 03-17-2023, 01:52 PM

Quote:

Originally Posted by Flynt

I got it! Apparently the ground on the right side of the solenoid is what I needed to hook onto. It's not going anywhere else in the system... except for the fuse box which is also screwed into the main panel so it should or could all be on the same ground still??? I don't understand why the ground on the left side doesn't work... of course it does when I draw from that positive side of the solenoid but why would it cut out then? Would that mean it has a really low amperage limit?

In my experience when you have a solenoid that seems to be acting like a breaker from high current it is due to a bad ground somewhere in the system. Check your grounds and make sure there is no rust, everything is tight, and that the copper wiring isn't black or brown from overcurrent.

Whenever I tie anything aftermarket into a vehicles electric system I always beef up the main ground to deal with the extra amperage I'm adding to it. Can either replace the ground with a thicker one or just add an extra. Can find them premade at Autozone if you know the length or what I do is make my own out of 2 gauge jumper cables on amazon, ends up being cheaper than buying 2 gauge wire by itself, plus you get some spring clamps. I cut the two wires apart, cut to length, crimp/solder on some cable lugs, and there you go. Can go cheaper if you go to a scrap yard, they normally sell the jumper cables people keep in their trunk for $1 or $2.

Even if it doesn't fix your problem. Double checking and beefing up your grounds is never a bad thing.

Rwnielsen · 03-17-2023, 04:01 PM

One last question...are you hooking up to either of the two small terminals on the solenoid? One of those is grounded, typically right at the solenoid mounting bolt or a nearby threaded stud from the metal backing plate. The other is the signal from your ignition switch to energize the solenoid. If you tie into the ignition signal with any significant load it will, no doubt, trip its circuit breaker.

Flynt · 03-17-2023, 05:28 PM

Quote:

Originally Posted by Rwnielsen

One last question...are you hooking up to either of the two small terminals on the solenoid? One of those is grounded, typically right at the solenoid mounting bolt or a nearby threaded stud from the metal backing plate. The other is the signal from your ignition switch to energize the solenoid. If you tie into the ignition signal with any significant load it will, no doubt, trip its circuit breaker.

Yes, that is what I'm doing now. They both appear to be going to ground. The bigger wires go to my fuse box. I'm not sure at all how my ignition is wired into everything...

Rucker · 03-17-2023, 08:59 PM

Here's the thing: if the juice going to the diesel heater is flaky in any way, the diesel heater will reset.

This will frustrate you to no end.

My diesel heater is set up to automatically switch from house battery to shore power and back, but it resets when I pull off the shore power. Seems to handle going to shore power, but not the other way.

It's not good for that diesel heater to glitch out, and may result in premature failure of the heater, or worse, intermittent failure because it's getting clogged up with unburnt diesel.

Have you considered using a DCDC charger that draws from the alternator and just keeps your house batteries charged up?

And BTW my diesel heater draws close to 3 amps when running, but only about 8 amps when starting up. There may be a bit of an inrush or surge when it starts, but the glowplug and fan seem to settle down to about 8 amps while it winds up.

Rwnielsen · 03-17-2023, 09:44 PM

Quote:

Originally Posted by Flynt

Yes, that is what I'm doing now. They both appear to be going to ground. The bigger wires go to my fuse box. I'm not sure at all how my ignition is wired into everything...

When installed correctly and everything is off, your meter will read a ground through both of the small wires on the solenoid. That is just a coil winding. A decent meter will tell you ohms of resistance between the two but either way, those are not your tie in points. The two larger wires, one to the battery and the other to the fuseblock are what you're interested in.
In your picture there's a ground stud in the top left. That would be a great place for a ground from your heater. Personally, I'd ground it to the bus frame right where it's mounted as well.
Your power will then come from the large terminal that goes to the fuse block. Use a large, crimp type, ring terminal, under the large wire terminal. You should put your fuse in that general area as well.
Now...when you turn on the key you will have full voltage at your power feed wire and a redundant ground. That will work .

rossvtaylor · 03-18-2023, 09:06 AM

I just got to this thread and was reading through it...and wondering if the new connection was being made to the smaller "trigger" terminal on the solenoid. That's the only way it could be "tripping" as the added current through that small wire blew a fuse or opened a circuit breaker. The large gauge cable won't be affected by the added draw of a heater or such.

As others pointed out, the solenoid is just a switch and doesn't care how much current goes through the switched contact portion (to a point, of course). But the coil (trigger) circuit is another thing. The guidance RWNielsen gave you is right on...connect your new loads to the power (battery) side large terminal, with a proper ring terminal and a proper fuse, then you'll be golden.

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